(1) Field of the Invention
The invention relates to a color filter and testing method thereof, and particularly the color filter with features of low color shift and high contrast ratio.
(2) Description of the Prior Art
Following the advancement of display technology, compared to conventional CRT display, TFT-LCD (thin film transistor liquid crystal display) has become the main product because of the advantages of light, thin, low radiation and small size. Due to the rapid development of LCD products, manufacturers gets harder and harder competition.
A color filter (CF) is one of the most important components for LCD to display the color image. LCD uses liquid crystal molecules under different voltages to affect the polarized light to control gray level, and uses color filters to mix colors for different gray levels.
Color filters are usually manufactured by dispersing pigments. Under zero gray level, part-depolarization occurs because the pigment molecules affect polarized light which goes through the color filter. When polarized light goes through the upper polarizer, the polarizer has no way to absorb the polarized light completely so that a light leakage occurs.
However, different color pigments (red, blue and green) cause different levels of light leakage due to different particle sizes, so that color shift occurs in the dark state.
Generally, color filter manufactures regulate the proportion of the contrast ratios of red, blue and green photoresists for the requirement of lower color shift. However, the contrast ratio is required to increase with rising the image quality of LCD. It is very difficult to satisfy the requirement of low color shift under high contrast ratio.
In other words, above regulation of proportions is only applied to non-high contrast ratio. Under high contrast ratio, it cannot reduce the color shift.
Therefore, it is necessary to find some conditions for color filter to reduce color shift regardless of under high or low contrast ratios.